Applicator device



Oct. 29, 1968 G. l.. BEYER ET AL APPLICATOR DEVICE y 2 Sheets-Sheet 1 Filed OCt. 13, 1967 AGEA/T Oct. 29, 1968 G. L. BEYER ET AL APPLICATOR DEVICE 2 Sheets-Sheet 2 Filed Oct. l5, 1967 mx YN we NE m GEORGE L. BEYER WILL/AM C. YORK INVENTORS United States Patent Olce 3,407,786 Patented Oct. 29, 1968 3,407,786 APPLICATOR DEVICE George L. Beyer and William C. York, Rochester, N.Y., assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey Filed Oct. 13, 1967, Ser. No. 675,112 16 Claims. (Cl. 118-637) ABSTRACT OF THE DISCLGSURE A multiple slit applicator head for applying a liquiu composition to the surface of a moving web of material. The head is arranged in closely spaced relationship to the surface of the material and is provided with a plurality of spaced, parallel entry and exit slits arranged transverse to the direction of movement of the material. The entry slits permit the liquid composition to ow toward the surface and any excess is returned to a reservoir via the exit slits which are arranged between adjacent entry slits and in closer proximity to the one in a downstream direction. Such an arrangement of slits permits a continual replenishment of the liquid composition with uniform application thereof to the surface of the material.

Field of the invention This invention relates to a device for applying a liquid composition to the surface of a movable web of material and more particularly to a device for applying a liquid developer to vthe latent electrostatic image bearing surface of a xerographic material that is movable relative to the device.

Description ofthe prior art It is well known in the prior art to apply a liquid composition to the surface of a movable web of material -by means of a pad which is saturated with the liquid and in contact with the material or by means of a cylindrical surface which carries a liquid composition from a reservoir to the surface of the material on which the liquid composition is to be applied. In each of such applicator arrangements a pressure roll is usually employed to maintain the web of material in contact with the pad or cylindrical surface. In such arrangements, at any instant only a relatively small transverse area of the web of material is actually in contact with the liquid composition. To effect an even distribution of the liquid composition on the surface, particularly with the use of an applicator roll, a doctor blade is usually employed to remove excess liquid from the roll just prior to contacting the material. Even with such arrangements the liquid composition is often applied non-uniformly and with streaks of various thicknesses.

In the field of xcrography, the development of a latent electrostatic image on the surface of a photoconductive material can be accomplished by what is referred lto as liquid development. Such a liquid comprises an insulating liquid carrier in which charged toner particles are dispersed uniformly. As is well known, the particles are provided, in one mode of use, with a charge opposed to that carried by the image areas, so that the toner particles will adhere only to the image areas. In order to provide an optimum image, it is necessary that the toner particles be deposited uniformly throughout the image areas thereby providing a legible image of uniform density. The use of developer applicators in which rolls are used results in the same disadvantages as noted above, namely, that the developed image is streaked and that the resultant image is not consistently of uniform density. When a plate-type of developer head is used having a single, centrally located feed slit for applying the liquid developer to the image-bearing surface of the xerographic material, the movement of the photoconductive material across the developing head carries the developer with it. As the developer is carried farther from the slit by the moving material, the amount of toner in the developer decreases to the point where the carrier has very few, if any, toner particles left for transfer to the material before being separa-ted therefrom. The concentration of toner particles can be increased; however, when this is done, the background density increases because there are larger residues of toner particles in the uncharged areas. As the rate of development increases, that is, the rate of movement of the xerographic material increases, the development eiciency falls olf considerably rather than increasing. Since the spacing between the developer head and the image bearing surface is very small, the developer liquid therebetween is easily and very quickly depleted of its toner particles. Another disadvantage of a single slit developing head is the production of flow streaks in the finished print due to the depletion of the toner particles or their being collected at some downstream site. It is therefore desirable to produce a liquid developer head which will provide a developed image of maximum uniform density and with no background deposits or flow streaks.

Summary of the invention One object of the invention is to provide a multiple slit applicator head which is capable of applying a liquid composition to the surface of a moving web of material at a high rate of speed with uniform distribution of the liquid composition over the entire surface of the material.

Another object of the invention is to provide a multiple slit applicator head in which flow irregularities are substantially eliminated, thereby decreasing the possibility of forming ow streaks.

Still another object of the invention is to provide an applicator head for applying a liquid developer to the image-bearing surface of a xerographic material whereby an image of uniform and maximum toner particle density is obtained.

And yet another object of the invention is to provide an applicator head for applying a liquid developer to the image-bearing surface of a xerographic material in which the developer is continually replenished to provide maximum toner concentration throughout the entire period of contact of the developer with the image-bearing surface.

Other objects and advantages of the invention will be apparent Vto those skilled in the art when the more detailed description thereof is read in conjunction with the accompanying drawings.

In a preferred embodiment of the invention, the above objects of the invention are attained by an applicator 'head in which the image-bearing surface of -a web of xerographic material is moved relative to an Iapplicator head which supplies ya continuous ow of liquid developer to the surface. The applicator head comprises a base plate having a central well or cavity into which the liquid developer is continuously pumped from a reservoir or supply. A cover plate overlies the well and the exposed surface of the cover plate is arranged in closely spaced relationship to the image-bearing surface of the xerographic material. The liquid developer flows through 'a plurality of spaced parallel entry slits arranged transversely of the direction of movement of the material and toward the image-bearing surface. The cover plate is also provided with a plurality of open-end recesses each of which is parallel 4to and between adjacent entry slits for conducting any excess liquid developer to a return recess in the base plate. The developer flowing from the entry slits is carried by the surface of the xerographic material toward the next adjacent open-end recess into which the developer then flows. Immediately adjacent the openend recess is other entry slit which supplies more fresh developer tothe surface. This introduction of fresh developer and removal of used developer continues along the length of the head until the image 'areas on the surface have been developed uniformly. With an applicator head of this type, the exposure of thel image areas to fresh developer is increased by a factor dependent on the number of entry slits. Also,l lower concentrations of toner particles can beI used so that background density is minimized and an optimum development of the image areas is attained because of the continuous replacement `of depleted developer. It has been found that under certain conditions, the reflection density of lan image developed by means of an applicator head in accordance with the invention is increased by at least `a factor of three as compared to applicator heads of the single slit or roll type. Further, the resulting developed image has a uniform density and the plint background is free of any development or flow streaks.

Description of the drawing Reference is now made to the accompanying drawings wherein like reference numerals designate like parts and wherein:

FIG. 1 is a schematic representation showing an applicator head in accordance with the invention for applying la liquid developer to the image bearing surface of a xerographic material;

FIG. 2 is a plan view of the applicator head shown in FIG. 1;

FIG. 3 is avertical section through the applicator head taken substantially along line 3--3 of FIG. 2;

FIG. 4 is a vertical section taken substantially along the line 4 4 of FIG. 2 and showing the configuration of the entry slits;

lFIG. 5 is a vertical section taken substantially along the line 5-5 of FIG. 2 and showing the configuration of the exit slits; t

FIG. 6 is a partial side elevation of the cover plate of the applicator head showing a weir construction for altering the discharge ends of the exit slits; and

FIG. 7 is an enlarged cross-section through the entry and exit slits of the cover plate for showing by means of anrows the flow of liquid between the slits and the image bearing surface of the xerographic material.

Description of the preferred embodiment With reference to FIG. 1, a sheet or web 1t) of xerographic material is shown as being moved by two pairs of spaced rolls, 11, 12 and 13, 14 and into closely spaced relationship relative to an applicator head generally designated by the numeral 15. The image bearing surface of the xerographic material 10 faces the applicator 15 and can be maintained in such closely-spaced relationship by means of a guide plate 16. Obviously, the xerographic material 10 can be moved relative t-o head 15 by means other than rolls 11-14 including even manual movement.

The applicator` head 15 comprises a base plate or member and a cover plate 21, the exposed or outer surface 22 of the plate 21 facing the image bearing surface of xerographic material 10. In a manner to be described in detail hereinafter, the base yplate or member 20' is connected to a liquid reservoir 23 by means of a return line 24, the reservoir being connected to a pump 25 by means of line 26. The liquid in reservoir 23 is. therefore pumped into base member 20 via line 27 and can be considered as being under at least some pressure..The applicator head 15 as a unit can be adjusted relative to the xerographic material 10 by means of suitable adjustable supporting members or legs 30.

With particular :reference to FIGS. 2-5 the base plate 20 is shown as being rectangular in shape and is yprovided with a substantially central well or cavity 35, the crosssection of which is best shown in FIGS. 3 and 4. The well is surrounded by a land 36 which separates the well from a return recess 37. From FIGS. 3-5 it will be noted that the depth of return recess 37 varies with the high point at the upper right-hand corner as seen in FIG. 2 and the low point in the lower lefte'hand corner wherein an outlet- 38 is provided. The outlet 38 is connectable to line 24 for returning the excess liquid to the reservoir 23, the reservoir being provided with means not shown for maintaining a fixed concentration of toner particles in the liquid. Nell 35 is provided with an inlet 39 and a nipple 40 which can threadably engage base plate k2t) for receiving the flexible `or rigidv line 27 which connects the pump 25 to the applicator head 15.

The cover plate 21 corresponds in size and shape to the external configuration of the land 36 and is fixed thereto by means of screws 42. The cover plate 21 is provided with a plurality of entry slits which extend in `a direction transverse to the movement of the material as indicated by the arrow 46 in FIG. 2. With reference to FIG. 4, it will be noted that the slits 45 are closed at each end for retaining the liquid developer between the well 35 and the surface 22 of plate 21. The cover plate 21 is also provided with a plurality of exit slits 47 as shown in FIGS. 2 and 5. The shape of the Islits 47 is bestr shown in FIG. 5 wherein it will be noted that the slits are provided with open ends and diverge from a point generally central relative to plate 21 toward opposed sides thereof. With reference to FIG. 2 it will be noted that the exit slits 47 'are arranged between adjacent entry slits 45 and in closer proximity to the entry slit 45 in a downstream direction, that is, in the direction of arrow 46 and in the direction in which both the developer liquid and material are moved as explained in more detail herein-after.

On each of the opposite sides of plate 21 which are intersected by the exit slits 47, a plate 50 is slideably mounted by means of screws 51 that engage respective elongated slots 52, see FIG. 6. the plate 50 is provided with a plurality of notches 53 corresponding in spaced relation substantially to that of the exit slits 47, said notches having a shape such that the width or configuration of the` ends of exit slits 47 can be changed in accordance with the direction of lateral movement of the plate 50. By movement of the plate 50, the size of the open end of exit slits 47 can be altered to control the flow of liquid developer from the slits to the return recess 37.

With reference to FIG. 7, it will be seen that the liquid developer 32 is moved due to pump 25 from the well 35 through the entry slits 45 to the space between the surface 22 of plate 21 and the image bearing surface of the xerographic material 10. Since the xerographic material 10 is moving to the left, as seen in FIG. 7, it carries the developer liquid along the surface 22 and toward the next exit slit 47. Between a slit 45 and a slit 47 the toner particles carried by the `developer liquid are attracted to the charged image areas on the xerographicmaterial 10. At the next slit 45 downstream, that is, in the direction indicated by arrow46 in FIG. 2, fresh liquid developer is again brought into contact with the xerographic material. Aspreviously described, the excess liquid again ows out through the next adjacent slit 47. By this process of continually subjecting the xerographic material to fresh liquid developer, a uniformly developed image of maximum density is obtained. In the present disclosure, the xerogrphic material is actually subjected to six replenishments of liquid developer. By maintaining the width of the applicator head somewhat less than the width of the web or sheet of material to be treated, there is no possibility of wetting the back surface of the material. As shown in FIG. 7, the entry slits 45 are beveled or made divergent, as indicated by numeral 54, at each end or at least at the end adjacent surface 22 to increase the area of liquid developer in contact with the surface of the material `10.

It has been found that the density of the developed image can be controlled by applying a biasing potential 55 between the conductive backing support of the Xerographic material and the applicator head 15. For example, the potential 55 can be connected between base plate 20 and roll 11 which is conductive and engages the conductive backing support of xerographic material 10, see FIG. l. In this instance, the materials from which the applicator head is made must be electrically conductive. The magnitude and polarity of the bias is chosen so as to cancel the residual undischarged toe potential of the photoconductor so that it does not contribute to background development. Normally, a 50 volt bias applied to the development head and having the same polarity as the image charge is sufficient. Total reversal of the image, that is, negative-to-positive can be achieved by applying a bias nearly equal to the maximum image charge level. For example, if the xerographic material is uniformly charged to a positive 800 volts and then image- Wise exposed to form a charge image, a positive bias of 750 volts can be applied to the applicator head 15. The image can then be developed with positively charged toner particles. The use of a conducting applicator head facilitates the printing of solid area prints. By making base plate and cover plate 21 of insulating materials, the image can be fringer developed which allows greater exposure latitude and is particularly adapted to the making of line copy prints.

While the preferred embodiment of the invention has been described with respect to developing a xerographic image, the applicator head per se can be used for applying a liquid layer to any surface under conditions where continual replacement aids in maintaining the concentration of a component of the liquid or prevents buildup of a reaction product which might decrease the rate of a process. Also, the surface 22 of cover plate 21 can be arcuate in shape rather than planar in the event a roll is used in conjunction with applicator head 15. Such an applicator head can be used for processing 16 mm. or 35 mm. photographic tilm by the use of normal or viscous developers. Further, mcrosize applicator heads of the type disclosed can be made for striping magnetic sound material on amateur movie films. Very large units can be used to apply a liquid composition to webs of various widths at high transport rates. With a high transport rate, the active path length of the head can be increased with a corresponding increase in the number of entry and exit slits.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

We claim:

1. An applicator head for applying a liquid composition to the surface of a material movable relative to said head, comprising:

a member interconnected to a supply of said liquid composition and having a surface arranged to lie in closely spaced relationship to the surface of said material; and

a plurality of entry slits and a plurality of exit slits in said member that are arranged alternately in spaced and generally parallel relation to each other and transversely of the direction of movement of said material;

said entry slits being connected to said supply for permitting said liquid composition to flow into the space between said surface and the surface of said material for contacting the latter and said exit slits conducting any excess liquid composition away from said surface.

2. An applicator head in accordance with claim 1 including means for controlling the flow of said liquid composition from said exit slits.

3. An applicator head in accordance with claim 1 wherein each exit slit is arranged in closer proximity to the entry slit in a downstream direction relative to the direction of movement of said material.

4. An applicator head in accordance with claim 1 wherein the ends of said entry slits adjacent said surface are divergent for increasing the area of liquid composition in contact with the surface of said material.

5. An applicator head for applying a liquid composition to the surface of a web of material movable relative to said head, comprising:

a -base plate having a substantially central well connectable to a pressurized supply of said liquid composition and a return recess spaced from and surrounding said well and connectable to s-aid supply to return excess liquid thereto;

a cover plate overlying said well and having the exposed surface thereof arranged to lie in closely spaced relationship to the surface of said web;

a plurality spaced and generally parallel entry slits in said cover plate arranged transversely of the direction of movement of said web for interconnecting said -well to said surface to permit said liquid composition to flow toward and into contact with the surface of said web; and

a plurality of open-end recesses in said cover plate, each of which is generally parallel to and between adjacent entry slits for conducting any excess liquid composition to said return recess.

6. An applicator head in accordance with claim 5 wherein the cross-sectional area of said open-end recesses increases progressively from thecenter of said cover plate to the opposed side surfaces thereof.

7. An applicator head in accordance with claim 6 including an adjustable weir on each of the opposed sides of said cover plate for controlling the flow of said liquid composition from said open-end recesses.

8. An applicator head in accordance with claim 5 wherein each open-end recess is arranged in closer proximity to that adjacent entry slit which lies in a downstream direction relative to the direction of imovement of said material.

9. An applicator head for applying liquid developer to the latent electrostatic image bearing surface of a Xerographic material movable relative to said head, comprising:

a member interconnected to a supply of said liquid developer and having a planar surface arranged to lie in closely spaced relationship to said image bearing surface;

a plurality of entry slits and a plurality of exit slits in said member that are arranged alternately in spaced and generally parallel relation to each other and transversely of the direction of movement of said material;

said entry slits conducting said liquid developer into the space between said planar surface and the image bearing surface of said material for contacting the latter and said exit slits conducting any excess liquid developer away from said planar surface.

10. An applicator head in accordance with claim 9 wherein xerographic material includes an electroconductive layer and said member is electrically conductive, including means for imposing an electrical bias between said member and said electrically conductive portion to control the image density.

11. An applicator head in accordance with claim 9 including means for controlling the tiow of said liquid developer from said exit slits.

12. An applicator head in accordance with claim 9 wherein each exit slit is arranged in closer proximity to that adjacent entry slit which lies in a downstream direction relative to the direction of movement of said material.

13. An applicator head in accordance with claim 9 wherein at least the ends of said entry slits adjacent said planar surface are divergent for increasing the area of :liquid developer in contact with the surface of said web.

14. An applicator head for applying liquid developer to the latent electrostatic image :bearing surface of a xerographic material movable relative to said head, comprising:

a base plate having a generally central Well connectable to a pressurized supply of said liquid developer and a return recess spaced from and surrounding said Well and connectable to said supply for returning excess liquid developer thereto;

a cover plate overlying said -well and having the exposed surface thereof arranged to lie in closely spaced relationship to said image bearing surface of said material;

a plurality of spaced and generally parallel entry slits in said cover plate arranged transversely of the direction of movement of said xerographic material for interconnecting said Well to said planar surface to permit said liquid developer to flow toward and into contact with said image bearing surface;

a plurality of open-end recesses in said cover plate, each of which is generally parallel to and between adjacent entry slits and in closer proximity to that adjacent entry slit which lies in a downstream direction relative to the direction of movement of said material for conducting any excess liquid developer to said return recess; and

8 means disposed on said cover plate at the tenminating ends of the open-end recesses for controlling the ow of said liquid developer therefrom.

15. An applicator head in accordance with claim 14 wherein said xerographic material includes an electrocondu-ctive layer and at least said cover plate is electrically conductive, including means for Iimposing an electrical bias between said cover plate and said electrically conductive layer to control the image density.

16. An applicator head in accordance with claim 14 wherein at least the ends of said entry slits adjacent said planar surface are divergent for increasing the area of liquid composition in contact with said image bearing surface and said exit slits increase progressively in crosssectional area from the center of said cover plate to the opposed side surfaces thereof.

References Cited UNITED STATES PATENTS 3,027,821 4/ 1962 Wright 95-89 3,060,829 10/ 1962 Leighton et al. 95-89 3,149,550 9/1964 Lohse et al 95-89 3,196,832 7/1965 Zin 118-637 3,238,921 3/1966 Engelstad et al 118-637 3,342,164 9/1967 Lewis 118-410 XR PETER FELDMAN, Primary Examiner. 

